Different methods and feeding devices are known in the prior art for conveying particulate material at desired feeding rates into machines for further processing. One type of such feeding device incorporates a feeding belt for conveying particulate material at either a constant or a variable feeding rate. Control of the feeding rate in this kind of feeder is accomplished by controlling the speed of the feeding belt. However, the use of belt feeders in applications requiring uniform and accurate feeding rates presents problems. Various factors affecting performance of such feeders include the influence of wear and temperature in stretching or contracting the belt. Also, flexible materials must be used for belts and this limits the available materials. There are also problems regarding the accuracy of the feed rate since it is greatly dependent on the method used in depositing the material onto the belt. Also particulate material being conveyed may spill.
Other types of known feeders employ rotary feeding drums. One such example is a feeding drum disclosed in Boudwin U.S. Pat. No. 1,221,136 in which the feeding apparatus includes a revolvable feeding drum with a lifting vane located within the drum. Also, a structure of a rotatable feeder for conveying material to machines such as mills is disclosed in Holthoff U.S. Pat. No. 1,553,613. In rotary drum feeders, the material feeding rate is controlled by varying the rotational speed of the drum. Use of rotary drum structures has some advantages over belt feeders, including, inter alia, a greater variety of suitable materials for a rigid drum structure, and reduced criticality of mechanical adjustments than is required with belts.
In rotary drum type feeders, on the other hand, various mechanical parts are required, such as lifting vanes, spiral scopes, helical ribs, etc. for lifting and directing the particulate material from the rotary drum to the outlet means. The lifting vanes, helical ribs and other parts of the drum tend to abrade and wear and require maintenance.
There is thus a need in the art for a feeding apparatus with improved feeding accuracy, and a simpler and easier-to-maintain structure.